Although portable storage media such as universal serial bus (hereinafter denoted as USB) memories excel in portability, etc., they have the risk of information leak caused by the portable storage media that are lost or stolen. In order to avoid the above risk, the portable storage media are provided with, for example, a function of adding a lock function to an area where the data in the USB memories is stored and not canceling the lock function if authentication using passwords fails, a function of deleting data files upon occurrences of input errors of passwords, or a function of encrypting the entire area where the data in the USB memories is stored without the lock function and preventing the decryption if authentication using passwords fails.
In addition, for example, a technology disclosed in Japanese Lain-open Patent Publication No. 2006-338583 emerges as a computer-terminal storage medium capable of suppressing unauthorized use of data.